05000348/LER-2010-004
| Docket Numbersequential Revmonth Day Year Year Month Day Yearnumber No. 05000 | |
| Event date: | 10-29-2010 |
|---|---|
| Report date: | 12-14-2010 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3482010004R00 - NRC Website | |
Westinghouse -- Pressurized Water Reactor Energy Industry Identification Codes are identified in the text as [XX]
Description of Event
On October 29, 2010 at 14:00, it was determined that Unit 1 was not in compliance with Technical Specification (TS) 3.9.3 in that one penetration providing direct access to the outside atmosphere was not isolated while Core Alterations were in progress. Prior to commencing Core Alterations, refueling integrity was appropriately established per the site procedure on the inside of containment for this penetration. After Core Alterations commenced on October 28, 2010 at 05:35, a scheduled maintenance activity required shifting the integrity boundary to outside containment for this penetration. Refueling integrity was shifted to outside containment on October 28, 2010 at 23:38.
The governing site procedure for establishing refueling integrity was in error for this penetration and did not recognize the existence of two seal cooler vent valves [JM], configured in series, for the B train Residual Heat Removal (RHR) [BP] pump. After the maintenance replacement of the relief valve inside containment, it was discovered that the two seal cooler vent valves were open and provided direct access from the containment atmosphere to the auxiliary building during the time the relief was not installed. It is estimated that refueling integrity was lost for about 10 minutes during the relief valve replacement on October 29, 2010 at approximately 04:30.
Cause of Event
A latent procedure error existed in the site procedure governing refueling integrity when a design change for each RHR pump on each unit installed two additional seal cooler vent valves. Although plant drawings were appropriately updated, the impact to the refueling integrity procedure was not recognized.
Safety Assessment This event had no adverse effect on the safety and health of the public. There were no Safety System Functional Failures. The seal cooler vent valves, configured in series, were operable and either valve could have been closed to isolate the outside atmosphere from the effects of a fuel handling accident in containment.
A fuel handling accident did not occur during the short period of time refueling integrity was actually lost. All other containment penetrations complied with TS 3.9.3 and at least 23 feet of water was maintained above the reactor vessel flange during Core Alterations. Therefore, the safety and health of the public was not adversely affected during the limited time a direct path to outside atmosphere existed.
Corrective Action On October 29, 2010 at 14:00 when the seal cooler vent valves were discovered to be open, Core Alterations were already temporarily suspended for an unrelated problem with the Spent Fuel Pool bridge crane.
On October 29, 2010 at 15:20, containment integrity was moved back to inside containment when the relief valve was verified installed and intact per the site refueling integrity procedure. Core Alterations were recommenced on October 29, 2010 at 23:44.
The Unit 1 site procedure governing refueling integrity was corrected for both trains of RHR. The corresponding procedure on Unit 2 was also revised.
Additional Information
None